from collections import defaultdict, deque


def bellman_ford(n: int, adj: defaultdict):
    dists = [INF] * n
    dists[0] = 0  # 始点
    negative_nodes = set()  # 負閉路のノード
    for i in range(n):
        for v in range(n):
            if dists[v] == INF: continue
            for to, c in adj[v]:
                if dists[to] > dists[v] + c:
                    dists[to] = dists[v] + c
                    if i == n-1:
                        negative_nodes.add(to)

    return dists, negative_nodes


INF = 1 << 60
N, M = map(int, input().split())
A = list(map(int, input().split()))
adj = defaultdict(list)
r_adj = defaultdict(list)
for _ in range(M):
    a, b, c = map(int, input().split())
    a -= 1
    b -= 1
    adj[a].append((b, -(A[b] - c)))
    r_adj[b].append(a)


# 頂点 start から到達可能な頂点を求める
def find_reachables(start, adj):
    q = deque([start])
    used = set()
    while q:
        v = q.popleft()
        if v in used: continue
        used.add(v)
        for to in adj[v]:
            if to in used: continue
            q.append(to)
    return used


dists, negative_nodes = bellman_ford(N, adj)
reachables = find_reachables(N-1, r_adj)  # N-1 から到達可能なノード
if any(v in reachables for v in negative_nodes):
    print('inf')
else:
    print(-dists[N-1] + A[0])